A method for preparing a lithographic printing plate by means of ink jet printing is disclosed. The ink jet fluid contains an oleophilizing compound having in its chemical structure a boron containing group capable of reacting with the surface of a lithographic receiver.

The present invention relates to a method for the preparation of a lithographic printing plate by means of ink jet printing.
Traditional techniques of printing include letterpress printing, gravure printing and offset lithography. All of these printing methods require a plate, usually loaded onto a plate cylinder of a rotary press for efficiency, to transfer ink in the pattern of the image. In letterpress printing, the image pattern is represented on the plate in the form of raised areas that accept ink and transfer it onto the recording medium by impression. Gravure printing cylinders, in contrast, contain series of wells or indentations that accept ink for deposit onto the recording medium.
In the case of traditional offset lithography the image to be printed is present on a plate as a pattern of ink accepting (oleophilic) areas on an ink repellent (oleophobic or hydrophilic) background. In the wet system the required ink repellency is provided by an initial application of a dampening (or xe2x80x9cfountain) solution prior to inking. Conventional presensitized lithographic printing plates bear a UV sensitive coating based on photopolymer or diazonium chemistry. The plates have to be UV-exposed through a mask carrying the image. The mask is a graphic arts film prepared by photographic techniques based on silver halide chemistry and involving exposure by a camera or by an image-setter, and further involving wet processing. Depending on the type of plate used (negative or positive) the non-image areas or the image areas are solubilized thereby differentiating the plate into oleophilic and hydrophilic areas. A disadvantage of this traditional method is the necessary cumbersome preparation of the photographic intermediate film involving wet processing. A further drawback is the wet processing of the printing plate itself.
With the advent of the computer in revolutionizing the graphics design process leading to printing, there have been extensive efforts to develop a convenient and inexpensive computer-to-plate system wherein a photographic intermediate is no longer required. In recent years some of these systems are introduced into the market based on different chemical systems and exposure methods. For instance, the SETPRINT material, trade mark of Agfa-Gevaert N.V. is based on silver halide DTR chemistry and consists of a polyethylene terephthalate base carrying a photographic coating which after photo-mode exposure and processing produces complementary oleophilic and hydrophilic areas. Another system based on photo-mode exposure but with a hydrophilic aluminum base is LITHOSTAR, trade mark of Agfa-Gevaert N.V. A system based on heat mode exposure by means of an intense infra-red laser is called THERMOSTAR, also a trade mark of Agfa-Gevaert N.V.
Many of the new computer-to-plate systems are large, complex, and expensive. They are designed for use by large printing companies as a means to streamline the prepress process of their printing operations and to take advantage of the rapid exchange and response to the digital information of graphics designs provided by their customers. There remains a strong need for an economical and efficient computer-to-plate system for the many smaller printers who utilize lithographic printing.
A number of electronic, non-impact printing systems have been investigated for use in making lithographic printing plates to satisfy the needs of these smaller printers. Foremost among these have been laser printing systems, for example as described in U.S. Pat. No. 5,304,443 and references therein. Another non-impact printing system which has received attention for economical and convenient computer-to-plate preparation for lithographic printing is thermal transfer printing, for example, as described in U.S. Pat. No. 4,958,564.
In recent years, ink jet printers have replaced laser printers as the most popular hard copy output printers for computers. Some of the competitive advantages of ink jet printers are low cost and reliability. The ink jet printing system is a relatively rapid image output system and has a simple construction because it does not require any complex optical system. In recent times, there have been some reports in the literature proposing the use of ink jet printers to make lithographic printing plates.
In Japanese Kokai 62-25081, an oleophilic liquid or fluid ink was printed by ink jet printing onto a hydrophilic aluminum surface of a lithographic printing plate. Titanate or silane coupling agents were present in the ink.
An ink jet printing apparatus to make lithographic printing plates is described in PCT WO 94/11191. It is directed to depositing hydrophobic or hydrophilic substances on hydrophobic printing plates.
In U.S. Pat. No. 5,501,150, a fluid ink and hydrophilic media set containing materials to produce a silver-reducible image by ink jet printing are used to make a metallic silver image which, following wet processing to make the silver image sufficiently hydrophobic, is said to provide a lithographic printing plate.
Ink jet printing wherein the ink is a solid or phase change type ink instead of a liquid or fluid type ink is described in U.S. Pat. No. 4,833,486 to deposit a hot wax on a surface of an offset plate. Upon cooling of the wax, it solidifies, thereby providing a printing plate. Solid ink jet printing has serious disadvantages for lithographic plates in that the wax or resin image has limited durability due to its thermoplastic, chemical, and adhesive properties and the amount and rounded shape of the solidified ink jet droplet on the media do not have the intrinsic image resolution properties found in liquid ink jet printing.
There is also prior art in the use of ink jet printing to apply an opaque image or mask pattern to a photosensitive lithographic printing plate blank, as for example, in Japanese Kokai 63-109,052. The blank is then exposed through the ink jet imaged mask pattern and then processed by conventional means to provide a lithographic printing plate. This approach retains the materials and processing of conventional lithographic printing plates and only uses ink jet printing as an alternative for the photomask through which the conventional plates are exposed. Thus this approach adds to the complexity and expense of the platemaking process and does not depend on the ink jet ink image for the hydrophobic image of the plate. U.S. Pat. No. 5,495,803 describes a solid or phase change type of ink jet printing to form a photomask for a printing plate.
As a further example of the methods for preparing printing plates by using the ink jet printing system, Japanese Kokai Publication 113456/1981 proposes methods for preparing printing plates whereby ink-repelling materials (e.g. curable silicones) are printed on a printing plate by ink jet printing. The printing plate obtained by this method is an intaglio printing plate in which the ink-repelling material formed on the surface of the substrate serves as a non-image part. As a result, the resolution of the printed images at shadow area or reversed lines is not so good. Moreover, a large amount of ink is needed in this method because the ink-repelling material must be deposited on the whole non-image part which occupies most of the surface of the printing plate, thereby delaying the printing process.
U.S. Pat. No. 5,511,477 discloses a method for the production of photopolymeric relief-type printing plates comprising: forming a positive or a negative image on a substrate by ink jet printing with a photopolymeric ink composition, optionally preheated to a temperature of about 30xc2x0-260xc2x0 C., and subjecting the resulting printed substrate to UV radiation, thereby curing said ink composition forming said image. This is an obnoxious method due to the sometimes high vapour pressure and toxicity of said inks.
U.S. Pat. No. 5,312,654 discloses a method for making lithographic printing plates comprising: forming an image on a substrate having an ink absorbing layer and a hydrophilized layer between the substrate and the absorbing layer by ink jet printing using a photopolymerizable ink composition, and exposing it to an actinic light in the wavelength region with which said ink composition is sensitized to cure the image. The printing endurance of said printing plates is low.
Japanese Kokai Publication 69244/1992 discloses a method for making printing plates comprising the steps of forming a printed image on a recording material subjected to a hydrophilic treatment by ink jet printing using a hydrophobic ink containing photocurable components, and exposing the whole surface to actinic light. However, the surface of the substrate to be used for the lithographic plate is usually subjected to various treatments such as a mechanical graining, an anodizing or a hydrophilic treatment to obtain good hydrophilic property and water retention property. Therefore, even the use of an ink composition having a very high surface tension results in a poor image on the surface of the substrate because of ink spreading and low printing endurance.
EP-A-533 168 discloses a method for avoiding said ink spreading by coating the lithographic base with an ink absorbing layer which is removed after ink printing. This is an uneconomical and cumbersome method.
Research Disclosure 289118 of May 1988 discloses a method for making printing plates with the use of an ink jet wherein the ink is a hydrophobic polymer latex. However said printing plates have a bad ink acceptance and a low printing endurance.
EP-A-003 789 discloses a process for the preparation of offset printing plates by means of an ink jet method with oleophilic inks. There is not indicated how said inks are made but from the examples it is clear that it concerns artificial latices, which are difficult to prepare.
JN-57/038142 discloses a method of preparing a printing plate by forming an ink image on a blank printing plate, and also by fixing this image thermally by making toner to adhere to this image-formed area. The composition of the ink is not mentioned, only the composition of the toners is disclosed.
JN-07/108667 discloses a plate-making method forming an ink image containing a hydrophilic substance on a conductive support whose surface layer is made hydrophilic according to an electrostatic attraction type ink set system to dry or cure the same, by applying bias voltage to the conductive support at the time of ink jet writing. This is a cumbersome process.
U.S. Pat. No. 5,213,041 discloses a method for preparing a reusable printing plate for printing, projecting an imaging deposit on the plate surface by jet printing using an ejectable substance containing a heat fusible component. The image forms an imaging deposit which is fused to the surface of the printing plate using a variable frequency and variable power induction heater.
In WO 97/43122 a lithographic printing plate is manufactured by means of an ink jet fluid comprising reactive components selected from the group consisting of transition metal complexes and organic carbonyl compounds. In a preferred embodiment the reactive compound comprises one or more chromium complexes of an organic acid.
The present invention extends the teachings on the preparation of a lithographic printing plate whereby an oleophilizing fluid is directly applied onto a lithographic receiver by means of ink jet printing.
It is an object of the present invention to provide a simple and inexpensive method for the manufacturing of a lithographic printing plate.
It is a further object of the present invention to provide a method for the preparation of a lithographic printing plate that requires no intermediate graphic film.
It is a further object of the present invention to provide a method for the preparation of a lithographic printing plate that requires no processing.
It is still a further object of the present invention to provide a method for the preparation of a lithographic printing plate that produces little or no waste and is therefore advantageous from the viewpoint of ecology.
It is still a further object of the present invention to provide a method for the preparation of a lithographic printing plate whereby the manufacturing steps can be performed in daylight.
Further objects will become clear from the description hereinafter.
The above mentioned objects are realized by providing a method for the preparation of a lithographic printing plate, said method comprising dispensing information-wise by means of ink jet printing droplets of a fluid onto a surface of a lithographic receiver, characterized in that said fluid contains an oleophilizing compound having in its chemical structure a boron containing group capable of reacting with said surface of said lithographic receiver. Preferably said agent is a boronic acid.
The different components used in accordance with the method of the present invention will now be explained in detail.
The essence of the present invention is the presence in the ink jet fluid of an oleophilizing compound having in its chemical structure a boron containing group capable of reacting with said surface of said lithographic receiver.
Preferably said compound is a boronic ester or boronic acid represented by following general formula (I):
wherein R1 is selected from the group consisting of a substituted or unsubstituted, saturated or unsaturated aliphatic chain, a substituted or unsubstituted aryl or heteroaryl group; R2 and R3 are independently selected from a hydrogen, a counterion to compensate negative charge, a substituted or unsubstituted, saturated or unsaturated aliphatic chain, a substituted or unsubstituted aryl or heteroaryl group; all R-groups may form rings with each other
In a more preferred embodiment, the compounds are boronic acids whereby R2 and R3 are hydrogen.
Typical examples of general formula I are given in table I:
Some boronic acids are commercially available. The other boronic acids can be prepared according to well documented procedures in the literature. Hydroboration of a double or triple bond is a typical synthetic strategy. Typical hydroboration reagents are catechol borane (J. Org. Chem. 60, 3717-3722 (1995), J. Am. Chem. Soc. 97(18), 5249-5255 (1975)), HBBr2SMe2 (Langmuir 10(7), 2228-2234 (1994)) and pinacol borane (J. Org. Chem. 57, 3482-3485 (1992)). Hydroborations can be catalyzed e.g. by Sm(III) (J. Org. Chem. 58, 5307-5309(1993)) or Rh-compounds (J. Am. Chem. Soc.121, 2696-2704 (1999)). Another synthetic strategy makes use of organometallic compounds, which are reacted with borate ester, or boron chlorides (J. Org. Chem. 54, 2179-2183 (1989), J. Org. Chem. 59, 6391-6394 (1994), J. Chem. Soc., Chem. Commun. 1998, 9, 1047-1048, Tetrahedron 54(26), 7465-7484 (1998)). Among others, a Pd(0)-catalyzed reaction between alkoxy-diboron derivatives and an arylhalogenide is a third possible strategy for the preparation boronic acid or esters as described in J. Org. Chem. 60, 7508-7510 (1995). As can be seen from this limited overview of possible preparations, boronic acids and esters are readily accessable compounds.f
Other useful oleophilizing compounds with a boron containing functional group, which are no boronic acids or esters, are given below. These compounds are well known as catalysts in asymetric organic synthesis:
These type of compounds are described in J. Am. Chem. Soc. 109, 7925 (1987), J. Am. Chem. Soc. 116, 3151 (1994) and Tetrahedron Lett. 1992, 33, 6907.
The oleophilizing agent may be present in the ink in an amount from 0.01 to 6, preferably from 0.02 to 3% by weight.
It is necessary that the oleophilizing agent is in the form of a homogeneous solution or a stable colloidal dispersion, so that it can pass through the nozzles of the printer head.
The liquid carrier is water or an organic solvent or combinations thereof. Choice of the specific liquid carrier depends on the specific ink jet printer and its compatibility with the ink jet printing head and cartridge being used for the ink jet printing. Both aqueous based and solvent-based fluids can be used in the present invention depending on the ink jet technology that is being used: piezo, thermal, bubble jet or continuous ink jet.
While water is the preferred medium for aqueous inks, the aqueous composition may comprise one or more water miscible solvents e.g. a polyhydric alcohol such as ethylene glycol, diethylene glycol, triethylene glycol or trimethylol propane. The amount of aqueous carrier medium in the aqueous composition may be in the range from 30 to 99.995, preferably from 50 to 95% by weight.
Also, organic solvents may be used as a carrier medium for the ink jet fluid, e.g. alcohols, ketones or acetates.
As known for the ink jet technology, the jet velocity, separation length of the droplets, drop size and stream stability is greatly affected by the surface tension and the viscosity of the aqueous composition. Ink jet fluids suitable for use with ink jet printing systems may have a surface tension in the range from 20 to 60, preferably from 30 to 50 dyne/cm. Control of surface tensions in aqueous ink jet fluids may be accomplished by additions of small amounts of surfactants. The level of surfactants to be used can be determined through simple trial and error experiments. Several anionic and nonionic surfactants are known in the ink jet art. Commercial surfactants include the SURFYNOL TM series, trade mark from Air Products; the ZONYL TM series, trade mark from DuPont; the FLUORAD TM series, trade mark from 3M, and the AEROSOL TM series, trade mark from Cyanamid. The viscosity of the fluid is preferably not greater than 20 mPa.s, e.g. from 1 to 10, preferably from 1 to 5 mPa.s at room temperature.
The ink jet fluid may further comprise other ingredients. A co-solvent may be included to help prevent the ink from drying out in the orifices of the print head. A biocide may be added to prevent unwanted microbial growth that may occur in the ink over time. Additional additives that may be optionally present in the ink include thickeners, pH adjusters, buffers, conductivity enhancing agents, drying agents and defoamers.
In order to enhance the image contrast after jetting the image on a lithographic receiver dyes may be added. Many dyes and pigments are known to be suited for the ink jet technology. Suitable dyes are further selected based on their compatibility in the carrier medium (i.e. aqueous based or solvent based) and on the compatibility with the oleophilizing agent, i.e. they should not lead to coagulation. Especially favoured for aqueous inks are anionic dyes such as acid black.
The support may be any support suitable for printing plates. Typical supports include metallic and polymeric sheets or foils. Preferably, a support having a metallic surface is used. Preferably, the metallic surface is oxidised. In a particularly preferred embodiment of the invention, a support having an anodised aluminium surface is employed. The support for the lithographic printing plate is typically formed of aluminium which has been grained, for example by electrochemical graining, and then anodised, for example, by means of anodising techniques employing sulphuric acid and/or phosphoric acid. Methods of both graining and anodising are very well known in the art and need not be farther described herein. After writing the image the printing plate can be inked with printing ink in the normal way, and the plate can be used on a printing press. Before inking the plate can be treated with an aqueous solution of natural gum, such as gum acacia, or of a synthetic gum such as carboxymethyl cellulose, as it is well known in the art of printing.
According to another mode in connection with the present invention the lithographic base with a hydrophilic surface comprises a flexible support, such as e.g. paper or plastic film, provided with a cross-linked hydrophilic layer. A particularly suitable cross-linked hydrophilic layer may be obtained from a hydrophilic binder cross-linked with a cross-linking agent such as formaldehyde, glyoxal, polyisocyanate, melamine type cross-linkers, ammonium zirconyl carbonate, titanate crosslinkers, or a hydrolysed tetraalkylorthosilicate. The latter is particularly preferred.
As hydrophilic binder there may be used hydrophilic (co)polymers such as, for example, homopolymers and copolymers of vinyl alcohol, acrylamide, methylol acrylamide, methylol methacrylamide, acrylate acid, methacrylate acid, hydroxyethyl acrylate, hydroxyethyl methacrylate or maleic anhydride/vinylmethylether copolymers. The hydrophilicity of the (co)polymer or (co)polymer mixture used is preferably the same as or higher than the hydrophilicity of polyvinyl acetate hydrolyzed to at least an extent of 60 percent by weight, preferably 80 percent by weight.
A cross-linked hydrophilic binder layer used in accordance with the present embodiment also can contain colloidal inorganic pigments that increase the mechanical strength and the porosity of the layer e.g. metal oxide particles which are particles of titanium dioxide or other metal oxides. It is believed that incorporation of these particles gives the surface of the cross-linked hydrophilic layer a uniform rough texture consisting of microscopic hills and valleys which serve as storage places for water in background areas. Preferably these particles are oxides or hydroxydes of beryllium, magnesium, aluminium, silicon, gadolinium, germanium, arsenic, indium, tin, antimony, tellurium, lead, bismuth, titanium or a transition metal Particularly preferable inorganic particles are oxides or hydroxides of aluminum, silicon, zirconium or titanium, used in at most 75% by weight of the hydrophilic layer. The inorganic pigments may have have a particle size ranging from 0.005 xcexcm to 10 xcexcm.
The thickness of a cross-linked hydrophilic layer in a lithographic base in accordance with this embodiment may vary in the range of 0.2 to 25 xcexcm and is preferably 1 to 10 xcexcm.
Particular examples of suitable cross-linked hydrophilic layers for use in accordance with the present invention are disclosed in EP-A 601240, GB-P 1419512, FR-P 2300354, U.S. Pat. No. 3,971,660, U.S. Pat. No. 4,284,705 and EP-A 514490.
As flexible support of a lithographic base in connection with the present embodiment it is particularly preferred to use a plastic film, e.g. subbed polyethylene terephthalate film, subbed polyethylene naphthalate film, cellulose acetate film, polystyrene film, polycarbonate film etc. The plastic film support may be opaque or transparent.
In ink jet printing tiny drops of ink fluid are projected directly onto an ink receptor surface without physical contact between the printing device and the receptor. The printing device stores the printing data electronically and controls a mechanism for ejecting the drops image-wise. Printing is accomplished by moving the print head across the paper or vice versa. Early patents on ink jet printers include U.S. Pat. No. 3,739,393, U.S. Pat. No. 3,805,273 and U.S. Pat. No. 3,891,121.
The jetting of the ink droplets can be performed in several different ways. In a first type of process a continuous droplet stream is created by applying a pressure wave pattern. This process is known as continuous ink jet printing. In a first embodiment the droplet stream is divided into droplets that are electrostatically charged, deflected and recollected, and into droplets that remain uncharged, continue their way undeflected, and form the image. Alternatively, the charged deflected stream forms the image and the uncharged undeflected jet is recollected. In this variant of continuous ink jet printing several jets are deflected to a different degree and thus record the image (multideflection system).
According to a second process the ink droplets can be created xe2x80x9con demandxe2x80x9d (xe2x80x9cDODxe2x80x9d or xe2x80x9cdrop on demandxe2x80x9d method) whereby the printing device ejects the droplets only when they are used in imaging on a receiver thereby avoiding the complexity of drop charging, deflection hardware, and ink recollection. In drop-on-demand the ink droplet can be formed by means of a pressure wave created by a mechanical motion of a piezoelectric transducer (so-called xe2x80x9cpiezo methodxe2x80x9d), or by means of discrete thermal pushes (so-called xe2x80x9cbubble jetxe2x80x9d method, or xe2x80x9cthermal jetxe2x80x9d method).
The present invention will now be illustrated by the following examples without however being limited thereto.


A method of producing a coating of solvent-free pressure-sensitive adhesive systems on substrates, especially release-coated substrates, in which the pressure-sensitive adhesive system is applied in one or more layers to a rotating roller by means of an adhesive applicator, the pressure-sensitive adhesive system on the roller is crosslinked in an irradiating means by means of high-energy radiation, and the roller is contacted with the substrate, so that the pressure-sensitive adhesive system is transferred from the roller to the substrate.

The invention concerns a method of producing a coating of solvent-free pressure-sensitive adhesive (PSA) systems on substrates, especially release-coated substrates, the operation of coating running by way of a roller. While the PSA system is on the roller, the applied adhesive film is crosslinked using electron beams (EB), UV or IR rays.
From the prior art it is known that in order to obtain PSA films possessing high shear resistance it is preferable to employ acrylic PSAs which are crosslinked by methods which include physical methods. In the case of EB and UV radiation, the desired product properties are adjusted by way of the radiation dose; in the case of IR radiation, by way of the product temperature and the residence time.
According to the methods known to date, PSA films are coated directly or indirectly onto release-coated or non-release-coated substrates with the aid, inter alia, of multiroller applicators, single-manifold, slot or multiple-manifold dies and are then subjected to the crosslinking operation.
For products comprising a coating to be crosslinked, which may be a PSA, for example, and a radiation-degradable backing, such as paper, cellulose wovens or nonwovens, and PP films, for example, it is possible to minimize the damage by optimizing the accelerating voltage. When this is done, the backing receives a significantly lower average dose than the coating, while the fall in dose in the coating remains within acceptable limits.
Relationships of this kind are described, inter alia, in EP 0 453 254 B (Yarosso et al.) and also in the paper accompanying a lecture given by Dr. Karmann at the 7th Munich Adhesives and Finishing seminar, 1982.
As a basis for the calculation there is used, for example, the following empirical formula, which was published by Neuhaus-Steinmetz at RadTech Europe, Mediterraneo 1993.                               D                                [            %            ]                          =                              exp                                      {                              -                                                      (                                                                                18.8                          *                          X                                                                                (                                                          U                              B                                                        )                                                    1.57                                                                    -                      0.7                                        )                                    2                                            }                                            1            +                                          (                                                      9.7                    *                    X                                                                              (                                              U                        B                                            )                                                              1                                                                    xe2x80x83                                                                  57                                                                      )                            15
where
D is the dose in %
UB is the accelerating voltage in kV
X is the irradiated weight per unit area in g/m2, consisting of the weight per unit area of the vacuum window, the air gap between vacuum window and product, and the depth in the product
A double-sided adhesive tape consisting of a backing with the adhesive compositions, intended for crosslinking, on both sides and of an antiadhesively treated release liner, when irradiated uniformly from one side with accelerated electrons, may receive a maximum dose of only about 20 to 40 kGy; otherwise, the release liner has to be replaced owing to the unacceptable deterioration of the mechanical and antiadhesive properties. The maximum permissible absorbed radiation dose is dependent on the type of the PSA and of the release coatings.
Here too, a reduction in the unwanted effects can be achieved, at appropriate layer thicknesses, by means of a skillful choice of the accelerating voltage if the radiation dose in the release liner has already fallen significantly. However, in this case it must be borne in mind that the PSA layer facing the release liner must still receive a radiation dose which is sufficient for crosslinking.
When a double-sided adhesive tape comprising a backing with PSA compositions on both sides and of an antiadhesively treated release liner is irradiated symmetrically from both sides, it receives the full radiation dose. The same applies to what are known as transfer tapes, where the PSA to be crosslinked is coated onto a release liner without a further backing.
It is clear from the above that the necessary complexity for the crosslinking of double-sided adhesive tapes with electron beams becomes considerable when the radiation doses required to crosslink the PSA layer are so high that the mechanical and antiadhesive properties of the release liner are adversely affected to an unacceptably high degree, since then the release liner must be replaced by a new, unexposed liner, by relining.
The crosslinking of adhesive compositions on temperature-sensitive backings, such as unplasticized PVC or PP spunbondeds, for example, requires thermal crosslinking in a tunnel or with IR lamps. UV crosslinking at higher doses necessitates greater technological complexity or lower running speeds.
If the increase in the attainable cohesiveness of the adhesive films is not to be achieved by way of a correspondingly high radiation dose, then the high molecular weight of the adhesive can be attained by means of suitable polymerization techniques selected in accordance with the prior art.
Acrylic PSAs prepared in this way, however, possess a high resilience, which makes coating by standard methods such as multiroller application or die coating more difficult.
WO 97/15722 describes a process used to bring about relaxation of the adhesive film directly following its emergence from a single or multiple-manifold die. The disadvantage of this process is that the free path which the adhesive film emerging from the die requires in order to relax increases with rising molecular weight. This in turn has the consequence that the adhesive film pulls itself in to a greater or lesser extent, relative to the film width originally dictated by the exit width of the dies (a phenomenon known as neck-in). The consequence is that, in order to achieve required adhesive film coating widths, there is a need for die widths which must be made wider, by some extent, than is the case with the present invention, since in this case lower molecular weights may be compensated by higher radiation doses.
It is an object of the present invention to provide a method of producing a solvent-free pressure-sensitive adhesive coating on substrates, especially release-coated substrates, which avoids the disadvantages of the prior art and which permits cost-effective manufacture and the use of radiation-chemical crosslinking, especially with accelerated electrons or UV radiation, without the need to accept damage to the backing and to the release liner.
This object is achieved by a method as specified in the main claim. Advantageous embodiments of the method are the subject of the dependent claims.
The invention accordingly describes a method of producing a coating of solvent-free pressure-sensitive adhesive systems on substrates, especially release-coated substrates, in which
the pressure-sensitive adhesive system is applied in one or more layers to a rotating roller by means of an adhesive applicator,
the pressure-sensitive adhesive system on the roller is crosslinked in an irradiating means by means of high-energy radiation, specifically using electron beams (EB), UV or IR rays, and
the roller is contacted with the substrate, so that the pressure-sensitive adhesive system is transferred from the roller to the substrate, and if desired is rolled up.
Typical irradiating means employed in the context of the inventive embodiment of the method are linear cathode systems, scanner systems or multiple longitudinal cathode systems, where the equipment in question comprises electron beam accelerators.
The acceleration voltages are situated in the range between 40 kV and 350 kV, preferably from 80 kV to 300 kV. The output doses range between 5 and 150 kGy, in particular from 20 to 90 kGy.
As UV crosslinking units it is possible in particular to employ two medium-pressure mercury lamps each with an output of 120 W/cm or one medium-pressure mercury lamp having an output of 240 W/cm. The doses set are preferably from 10 to 300 mJ/cm2.
The contacting of the substrate takes place in particular by way of a second roller. Substrates used include papers, films, nonwovens and release-coated materials such as release papers, films, and the like.
The second roller, also referred to as the contact roller, preferably has a rubber coating and is pressed against the roller with a linear pressure of preferably from 50 to 500 N/mm, in particular from 100 to 200 N/mm. The contact roller preferably has a Shore hardness (A) of 40-100, in particular a Shore hardness of 60-80 shore (A). The substrate is preferably brought into contact with the roller in such a way that the speed of the roller surface coincides with that of the substrate. Where, however, it is intended that a reduction in thickness should take place along with the reception of the adhesive film, the substrate may also have a higher speed.
In a first advantageous embodiment, the roller is a steel roller, a chrome-plated steel roller, a rubber roller or a silicone rubber roller and/or is manufactured from elastic material. Furthermore, the roller may be smooth or may have a slightly structured surface. The smooth roller may preferably have a chrome coating. Optionally, the chrome-plated steel roller may possess a high-gloss-polished surface with a roughness Rz less than +/xe2x88x921 xcexcm. The coating roller may, however, also be rubberized, preferably with a rubber hardness of from 40 to 100 shore (A), in particular with a hardness of 60-80 shore (A). The roll coating may, in accordance with the prior art, comprise EPDM, Viton or silicone rubber, or other elastic materials.
It has also proven advantageous for the roller to be temperature-controllable, preferably in a range from xe2x88x9210xc2x0 C. to 200xc2x0 C., with very particular preference from 2xc2x0 C. to 50xc2x0 C.
The placement of the pressure-sensitive adhesive system onto the roller takes place in particular by means of a single or multiple-manifold die or a slot die.
In a further advantageous embodiment of the method, before the pressure-sensitive adhesive system is applied to the rotating roller, a fluid film is brought onto the roller, so that the fluid film is located between the roller and the pressure-sensitive adhesive system.
The fluid film is preferably water and/or distilled water, with or without additions such as alcohol, wetting agents and/or agents insensitive to the adhesive formulation, such as plasticizers or liquid aging inhibitors.
To achieve uniform wetting, the surface tension of the fluid should be lower than the surface tension of the roller to be wetted.
The fluid-laden roller is preferably coated contactlessly with the adhesive film emerging from the die. The distance of the die from the roller may be preferably from 0 to 60 mm, in particular from 1 to 10 mm.
Furthermore, the fluid applicator should also be temperature-controllable, in order to bring agents which are present in but insensitive to the adhesive formulation to temperatures associated with desired fluid properties.
The fluid may be wiped on or carried on; it is, however, also possible for the fluid to be brought onto the roller contactlessly, by spraying, for example.
In another advantageous embodiment of the invention, the radiation-chemical crosslinking is assisted by thermal crosslinking, which can be regulated by way of the temperature of the coated roller.
As the pressure-sensitive adhesive (PSA) system, use is made in particular of acrylic, natural rubber, synthetic rubber or EVA adhesives.
Examples of low molecular mass acrylic hotmelts employed include copolymers of (meth)acrylic acid and esters thereof having from 1 to 25 carbon atoms, maleic, fumaric and/or itaconic acid and/or their esters, substituted (meth)acrylamides, maleic anhydride, and other vinyl compounds, such as vinyl esters, especially vinyl acetate, vinyl alcohols and/or vinyl ethers.
The acrylic hotmelts may further be blended with one or more additives such as aging inhibitors, crosslinkers, light stabilizers, ozone protectants, fatty acids, resins, plasticizers, and accelerators.
Furthermore, they may have been filled with one or more fillers such as fibers, carbon black, zinc oxide, solid microbeads, silica, silicates, and chalk, the addition of blocking-free isocyanates also being possible.
In the case of rubber/synthetic rubber as starting material for the adhesive, further variation possibilities exist, whether the said material is from the group of the natural rubbers or the synthetic rubbers or whether it comprises any desired blend of natural rubbers and/or synthetic rubbers, it being possible to select the natural rubber or the natural rubbers, in principle, from all available grades, such as, for example, crepe, RSS, ADS, TSR or CV grades, depending on the required purity and viscosity level, and it being possible to select the synthetic rubber or synthetic rubbers from the group consisting of randomly copolymerized styrene-butadiene rubbers (SBR), butadiene rubbers (BR), synthetic polyisoprenes (IR), butyl rubbers (IIR), halogentated butyl rubbers (XIIR), acrylic rubbers (ACM), ethylene-vinyl acetate (EVA) copolymers and the polyurethanes and/or blends thereof.
Also, preferably, it is possible to add thermoplastic elastomers with a weight fraction of from 10 to 50% by weight, based on the overall elastomer content, to rubbers in order to improve the processing properties.
As representatives, mention may be made at this point, in particular, of the particularly compatible styrene-isoprene-styrene (SIS) and styrene-butadiene-styrene (SBS) types. As tackifier resins to be added, it is possible without exception to use all known tackifier resins, including those described in the literature. As representatives, mention may be made of the rosins, their disproportionated, hydrogenated, polymerized, esterified derivatives and salts, aliphatic and aromatic hydrocarbon resins, terpene resins, and terpene-phenolic resins. Any desired combinations of these and other resins may be used in order to adjust the properties of the resultant adhesive composition in accordance with what is desired. Express reference may be made to the outline of the state of the art in the xe2x80x9cHandbook of Pressure Sensitive Adhesive Technologyxe2x80x9d by Donatas Satas (van Nostrand, 1989).
As plasticizers which are likewise to be added, it is possible to use all plasticizing substances known from adhesive tape technology. These include, inter alia, the paraffinic and naphthenic oils, (functionalized) oligomers such as oligobutadienes, oligoisoprenes, liquid nitrile rubbers, liquid terpene resins, vegetable and animal oils and fats, phthalates, and functionalized acrylates.
In accordance with the present invention, radiation-sensitive and heat-sensitive backing materials do not come into contact with the radiation sources.
Relaxation of the adhesive film may likewise be forgone, since the adhesive film immediately following its emergence from the die is stabilized in its state by crosslinking on the roller. By means of the present invention, significantly higher radiation doses are possible in order to raise the cohesiveness of hotmelt PSAs to the desired level.
The reasons for the advantages of the present invention are that there is no damage whatsoever to the substrates and release liners used, as a result of physical crosslinking methods, and also that high molecular mass adhesive films exhibit a sufficiently low level of relaxation, if any, as a result of direct irradiation on the roller.
In the text below the intention, using a figure and a number of examples, is to illustrate the invention without, however, wishing to subject it to any unnecessary restriction.

Method for producing a coating of solvent-free pressure-sensitive adhesive systems on especially release-coated substrates in conjunction with crosslinking of the pressure-sensitive adhesive system


A learning method to enhance long-term retention of a large number of learned facts or principles. The method presents items to a User repeatedly and, depending on the recall of the User, the time between presentations of a properly recalled item increases. Items being presented for the first time and those presented a subsequent time before being properly answered are designated Unseen Items and O-Level Items, respectively. During each Session, a raw score is assigned to the item (related to the User""s ability of recall with the item). When its raw score becomes sufficiently high, the item is considered a P-Level Item, after which it is presented less frequently and the rate of presentation continually decreases as the User demonstrates that he or she knows the correct response for the particular P-Level Item. The number of Sessions that are skipped before the particular P-Level item is re-presented to the User is based on the User""s Level L in recalling the correct answer to the item. In this way, known items are repeatedly presented to the User with an ever-increasing interval between presentations. If the User fails to recall the item, the Level of the item is decremented and the time to next presentation decreased. As the User is working with this method, the progress of the User is recorded in a form available for review.

1. Field of the Invention
The present invention relates generally to methods of education and in particular to methods of self-education. More particularly, the present invention relates to a method of teaching oneself a large number of facts or principles about any one of a number of topics. More particularly yet, the present invention relates to such a method that enhances the retention of learned material in long-term memory. Even more particularly, the present invention relates to such a method that incorporates structured repetition of learned material, wherein the time interval between repeated presentations of already-learned material increases after each successful recall of that material, and conversely, wherein that time interval decreases upon an unsuccessful attempt to recall that material. Most particularly, the present invention relates to such a method that automatically optimizes the rules for each individual, determining when new material and previously learned material shall be presented, such a method that produces a continually evolving quantitative evaluation of the user""s success in learning the material targeted for acquisition.
2. Description of the Prior Art
Some aspects of teaching have remained relatively unchanged for many years. Nearly every educated person in modern society has experienced a classroom setting in which a teacher directs a group of students through a text about a particular topic. Through the decades, such classroom lessons have sought to instill knowledge through the assignment of individual work, often in the form of homework. After a pre-determined amount of material has been covered, a test is administered to measure the students"" retention of and proficiency with that material. After the test, the class moves on to cover new material, devoting no further attention to the already-covered material, with the possible exception of an end-of-term final exam containing a teacher-selected fraction of the material covered during the term.
It has long been observed that the structuring of the traditional educational program reflects a conflict of interest on the part of those maintaining it. By that, it is meant that the bodies such as school boards that have the responsibility for the education of young people have to meet goals that may not be consistent with applying the best teaching methods to the students. The most critical of these goals is to see that the educational program makes the most efficient use of scarce resources. That is, one wishes to develop and administer a program that benefits the greatest number of students affected by it. By its nature, the resulting program best serves the students with an average learning speed, and in so doing will short-change those students who learn at a faster or slower rate than the average. In summary, it is noted that the traditional mass-education program, in teaching an entire group of students at a pace that is optimal for the average student, will fail to recognize that students come to school from a wide range of backgrounds, bringing with them a wide range of learning aptitudes. Unless the individual student""s deviation from the norm is large enough to be immediately recognized, teachers generally do not respond to that individual student""s unique needs, a situation that might be partially alleviated were there easily obtained measures of each student""s progress. The present unsatisfactory approach to the non-average-student""s education is becoming increasingly harmful because of the rapidly increasing quantity and diversity of information that a student must assimilate in order to be even moderately well-educated. In passing, it can be noted that a particular student can be an above-average learner in one discipline, average in another, and below-average in a third. Even within a particular discipline, one may learn and retain some material quickly and yet stumble over other types of material, the latter being learned only with much repetition and effort.
The problem set out above is one that has certainly been recognized before. Since at least the 1960s, individualized courses of instruction have been designed with the goal of giving each student the opportunity to learn and to be tested at his or her own pace. Indeed, the phrase xe2x80x9cprogrammed instructionxe2x80x9d was coined during that period to refer to that method of instruction wherein the student progresses at his or her own rate. The student is presented with mini-exams every few pages and the results of those mini-exams determine the next set of material that is to be presented to the student. In general, these programmed courses allow the student to leave behind material once he or she has demonstrated a familiarity with it, again with the exception of a comprehensive examination at the end of a portion of the course.
Although programmed instruction was used long before personal computers were available to help implement it, the present ubiquity of such computers has led to their use with such material. For example, Ho et al. (U.S. Pat. No. 5,727,951; issued Mar. 17, 1998) discloses a computer-aided programmed learning system that allows the student to work at an individual pace. Seifert (U.S. Pat. No. 5,904,485; issued May 18, 1999) also discloses a computer-aided learning system that presents to the student material to be learned and assesses the student""s mastery of it. If mastery is lacking, the system of Seifert will present the material in a different way.
The methods disclosed by Ho et al. and Seifert and others of that school of thought all have the drawback that the material to be learned, once mastered, is not presented again. Such approaches ignore the fact that, even though material may be well-learned at one point, it can subsequently be lost. Thus, a drawback inherent in both traditional classroom methods and in traditional programmed instruction (whether computer-based or not) is the failure to allow for a student""s memory loss and/or confusion that develops over time following his or her one-time mastery of a certain body of knowledge. This failure is the more striking given the general agreement by researchers that a student is likely to have forgotten a large proportion of learned material within months or even weeks after the material has been xe2x80x9cmastered.xe2x80x9d Such rapid forgetting happens in spite of the fact that human memory is capable of retaining information over decades, indeed over lifetimes of 100 years and more.
To recognize and compensate for a fading memory of learned material, it might be thought that presenting the student periodically with information that he or she has already xe2x80x9clearnedxe2x80x9d might be useful. One effort in this direction is disclosed by Collins et al. (U.S. Pat. No. 5,577,919; issued Nov. 26, 1996), which provides for re-asking questions that have already been answered correctly. In the method of Collins et al. the student is presented with a set of facts and asked to divide it into a first group containing already-known items and a second group containing facts not-as-yet known. A sequence generator then presents a mix of items to the student from the first and second groups. This approach is then repeated, with new material being continually introduced. In this way, there is some re-presentation of already-learned material, and this will have the effect of enhancing the student""s long-term retention. The Collins et al. method, however, does not control the frequency with which known facts are re-presented to the student and in particular does not respond to the level of proficiency being demonstrated by the student in responding to the repeated presentation of questions.
Therefore, what is needed is a method of instruction that allows a student to learn at his or her own pace and that leads to longer retention of that which was once learned, be it in school, in on-the-job training, or while the student is working on his or her own. What is also needed is such a method that can provide the student or the student""s teacher with a quantitative measure of the student""s progress in learning particular items.
It is an objective of the present invention to provide a programmed method that will allow a student to work at his or her own individual pace and that enhances long-term retention of learned items to a greater extent than provided by traditional programmed instruction. It is a further objective of the present invention to provide such a method that will generate a quantitative measure of the student""s progress with respect to individual items being studied.
The present invention achieves the first of its objectives through a method of instruction that presents previously learned items to the student at a repetition rate that reflects the proficiency the student has shown in his or her knowledge of those items. In particular, the method of the present invention questions the student on previously learned items with a frequency that is inversely related to the student""s demonstrated proficiency in remembering those items. The present invention achieves the second of its objectives by analyzing this same demonstrated proficiency and storing the results of that analysis for review by the student or his or her teacher.
The method of the present invention can be directed at learning (memorizing) lists of factual information. It can also be used to develop skill in rule-manipulation that is often referred to as xe2x80x9cproblem solvingxe2x80x9d and to develop a demonstrable proficiency in the knowledge of scientific concepts. Nevertheless, for definitiveness, most the following discussion will envision the information to be learned to consist of a list of facts rather than principles or problems to be solved. Here, the associated questions, then, require only short factual answers. The questions presented or to be presented will be referred to as xe2x80x9cquestionsxe2x80x9d or xe2x80x9citems.xe2x80x9d The response given by the user will be referred to as a xe2x80x9cresponsexe2x80x9d or xe2x80x9canswer.xe2x80x9d The method will occasionally be referred to as including a xe2x80x9cProgram.xe2x80x9d This Program will be whatever moves the user and the test material through the various steps necessary to apply the method.
The person using the method of the present invention will be referred to herein as the xe2x80x9cuserxe2x80x9d or the xe2x80x9cstudent.xe2x80x9d A person working with or overseeing the student""s efforts will be referred to as the xe2x80x9cteacherxe2x80x9d or the xe2x80x9cproctor.xe2x80x9d For definitiveness and simplicity, this initial discussion will be predicated on there being a single session each day.
Archetypal examples of the first type of targeted learning (assimilating lists of facts) would be (1) solar system facts (e.g., masses of the sun and all the planets, distances between the solar system objects, materials comprising the planets and their moons, etc.), (2) geopolitical facts about the countries of the world, (3) breeds of dogs, (4) the periodic table including oxidation potentials of atoms, etc. Obviously, there is no end to such lists; the choice of the particular ones over which mastery will be attempted by a particular individual will depend on that individual""s personal interests and/or obligations. In such an application, the material presented will consist of simple questions requiring straightforward factual answers. The format of the questions can be, alternatively, (1) simple text in the language of the user, (2) language-independent images, or (3) any other means by which a question can be conveyed to a user. For that matter, the question may be conveyed by a combination of such forms. The choice will in part be determined by the nature of the list of facts being dealt with. In the dog-breeds example, the image of a representative of a particular breed would probably be the best way of determining whether the user can recognize and name that particular breed.
Pursuing further the variety of means by which questions are presented in the method and answers given by the user, it is noted that modern electronic techniques, including those currently under development, vastly expand the range of these means. As a simple extension of the means discussed above, consider a computer-based approach to giving hints in the context of a list of geopolitical facts about the world""s countries, and in particular the item: What is the capital of France? The question could be presented in exactly that textual form. On the other hand, it might be presented by showing the user a map of France, with the location of Paris marked; it might be presented by showing one or more photographs taken within the City of Paris, starting with general street scenes and leading up to an image of Notre Dame or the Eiffel Tower. Concurrently or alternatively, the computer system used for applying the method could generate the music for xe2x80x9cApril in Paris,xe2x80x9d or smells characteristic of Les Halles, and so on. Answers could be conveyed by the user via a keyboard, via a spoken word or words, and even, perhaps (in the future) by his or her brain waves being sensed by one of the peripheral components of the computer. Alternatively, in the case of questions dealing with the parts of an automobile engine, the correct response required to: Where is the carburetor? could be given by moving and clicking the computer mouse appropriately, and similarly for pointing out the parts of the human brain, in another type of list.
The heart of the present invention lies in its protocol for determining how frequently items that have already been answered successfully will be re-presented to the student. In this regard, the simplest embodiment of the present invention can be described as follows.
The first step in applying the method is to choose the master collection (xe2x80x9ccollectionxe2x80x9d) of items to be learned. At the first session the method will select from this collection of items in an order predetermined by the creator of the collection. Since by definition it is the first session, none of these items will have been presented before. Assume that the student works until N items have been seen, and that he or she responds well to M of the N items. Those M items will then be labeled in such a manner that they will not be asked until the next session, Session 2.
In the second session, first the M items answered well during the first session will be presented, and then the N-M items not answered well will be presented.
Of the M items first presented during the second session, assume that P are well-answered. Those P are then labeled so that they will not be re-asked on the third session but will be asked (presented) on the fourth. Assume that the remaining M-P items are answered only moderately well. They will be labeled so as to be re-asked on the third session. In this way, items that are well-answered are seen less and less often.
The time-ordering of the different categories of items on the second session, as discussed above, is reflective of the pattern that is most desirable to follow. It is important (though not a limiting element of the method of the present invention) that the items scheduled for re-asking at a particular session be presented prior to those not so queued. This is because of the importance of reinforcing the knowledge of those items and the fact that it is impossible to predict when a session is to be prematurely terminated. (The items that have never been asked have the lowest priority, and are reserved for the end of a given session.)
It is envisioned that the user will continue with an item until it is answered correctly; only then can he or she move on to the next item. Also, as part of this method, there will in general be available to the user a mode, call it a xe2x80x9cdictionary modexe2x80x9d in which the entire collection of items can be reviewed along with their correct responses.
In order to discuss the method of the present invention in somewhat more general terms, several more terms will be defined. xe2x80x9cNegative-Levelxe2x80x9d(xe2x80x9cN-Levelxe2x80x9d) Items or xe2x80x9cUnseen itemsxe2x80x9d will be those that have never been presented, and have L=xe2x88x921. xe2x80x9c0-Levelxe2x80x9d items are those that have been presented but have not been answered well enough to be queued for presentation in some future session, and have L=0. Finally, xe2x80x9cPositive-Levelxe2x80x9d (xe2x80x9cP-Levelxe2x80x9d) items or xe2x80x9cQueuedxe2x80x9d Items are defined as those items that are to be asked in a particular session, and have Lxe2x89xa70. In the context of these definitions, when the method is first applied to a new collection of items, all of the items in the collection are Unseen items. Gradually, as the student answers the items, they are shifted to the collection of 0-Level items and, if answered proficiently, to the collection of P-Level items.
Each item in the set of P-Level items has associated with it both a xe2x80x9ctime to next presentationxe2x80x9d (coded by means of a variable called the xe2x80x9cLevel,xe2x80x9d or xe2x80x9cLxe2x80x9d), and a session on which it is to be tested (its xe2x80x9cSession to Test,xe2x80x9d or xe2x80x9cStoTxe2x80x9d). If an item from that set is presented to the user, there are three possible outcomes. A poor response will result in the time to next presentation being cut in half, a response with medium accuracy will result in no change to that time, and a highly-accurate response will double the time to next presentation.
Although for the basic method of the present application to be applied, it is not necessary to adhere to this xe2x80x9cpowers-of-twoxe2x80x9d approach, this is a particularly convenient means of spacing out the re-asking of items in the P-Level collection. It is to be noted that each P-Level item, after being re-asked, may be labeled so as to be asked more frequently, less frequently, or remain unchanged.
All items, even those that are extremely simple, have associated with them an additional parameter, namely the xe2x80x9cScorexe2x80x9d of the particular item (always vis a vis the particular user, of course). In order to provide even more flexibility to the discussion, a raw score SR and a weighted score Sw will be introduced. In this context, SR is the score assigned to an item as a result of the user""s answer at a particular time and Sw is the score that the item receives once it is combined in some way with the Sw that the item had prior to being asked that time.
The Score, in turn, is used to determine whether L should change, as a function of two thresholds, a lower and an upper threshold. If the value of the weighted score Sw is above the upper threshold, the Level (L) of that item will be increased; should Sw fall between the upper and lower threshold L will remain constant, and should Sw fall below the lower threshold as the result of poor performance by the user during a particular presentation, L will be decreased. If L decreases to zero the item will be moved back into the set of O-Level items.
In order to be a bit more quantitative with respect to the embodiment of the method wherein the a particular P-Level Item is re-asked every second, every fourth, every eighth, . . . every xe2x80x9c2s thxe2x80x9d session (L=1, 2, 3 . . . .), one might define a quantity T that is equal to the number of sessions that must elapse until the particular item is re-asked.
T={2Lxe2x88x921xe2x88x921},
where L=1, 2, 3, . . . for a given P-Level Item. Thus for a P-Level Item having a Level of L=2, one session will be skipped between each time that the particular P-Level Item is asked. Similarly, if the Level for a particular P-Level Item is 8, then T=255, meaning that 255 sessions will pass before that particular P-Level Item is re-asked. If (as a result of one or more sessions in which a P-Level Item was not answered sufficiently correctly) L for that P-Level Item has fallen to 0, that item is no longer treated as a P-Level Item.
Now combine the concept of a P-Level Item""s score and its Level L. To be specific, one embodiment of the method has scoring as follows. A Score of 1000 is assigned to each P-Level Item being presented. Assume, then, that a completely correct answer leaves the P-Level item""s Score at 1000, that a completely incorrect answer reduces it to 0, and that partial credit can lead to any Score between 0 and 1000. Assume further that there exists a set of rules in this embodiment such that any item emerging from being presented with a Score of 800 or higher has its Level L incremented by unity, with a score of 699 or less has its Level L (given that L greater than 0) decremented by unity, and with any score in between has its L value unchanged. Consider, in that embodiment, a P-Level Item being presented with L=8. If it emerges with a Score of 800 or higher, its L will increase to 9, meaning that 255 sessions will pass before the Item is re-presented; if the Score is 699 or less, its L will decrease to 7, meaning that only 63 sessions will pass before this particular P-Level Item is re-presented; and for a Score between 700 and 799, L remains unchanged and the Item will be re-presented after 127 sessions have passed.
In a variant on the just-described embodiment, the score of a P-Level Item can be weighted by the scores of that P-Level Item at the ends of all previous presentations.
As part of the approach just described, one may assign a starting score of zero to an Unseen Item, only giving it a Level L and a T value once its score at the end of a particular presentation rises above a particular threshold level . Once the threshold score has been attained for an item, it is re-classified as a P-Level Item and is assigned a Level of 1.
Note that within the context of the above commentary, once an item has reached the threshold score and a Level L of 1, then, if this item (now a P-Level Item) is correctly answered the next time it is presented, L is again increased by 1. Consider a P-Level Item that has been correctly recalled each of three times it was re-presented (after the threshold score had been attained). It now has a Level L of 4, meaning that T={23xe2x88x921)=7. I.e., seven sessions will pass before it is re-presented. Alternatively stated, the P-Level Item will next be presented on the eighth session following the session in which its L value was increased to 4. The P-Level Item""s Level L continues to increase as the user continues to give the correct answer each time that that P-Level Item is presented and, consequently, the number of sessions between the current session and the next time the Item is presented increases geometrically. In contrast, the student""s failure to answer the P-Level Item correctly will cause its L to decrease. If, after its L has fallen to unity, the user again fails to respond correctly to the P-Level Item, the item in question will be placed in the set of 0-Level items and presented according to other rules.
Although the method of the present invention is not necessarily a computer-based method, the method""s scope is certainly expanded by the use of a personal computer or a computer terminal within a larger computer network. Needless to say, the use of a computer offers great advantages in managing the necessary calculations and bookkeeping tasks required for effective presentation of the Items and evaluations of their scores and of overall scores for the user. If a computer is used, some means of communication or interface between the computer and the user is necessary. The computer must be able to present questions either implicitly or explicitly to the user, and the user must have some means of providing the answer. The computer may present some combination of text, images, sounds (including music), smells, tastes, or any other modality to which the user can respond. The interface between computer and user may involve a keyboard, computer mouse, touch screen, voice recognition, or any other means of communication, including brain waves, small muscle movements or eye movements. A natural language interface may be feasible if the interface employs text or voice.
As alluded to previously, rules are employed that govern the selection of Items to be presented in a given session. For example, P-Level Items are presented before O-Level Items, and P-Level Items with lower levels are presented before those with higher levels. Unseen Items would normally be selected for presentation based on a logical order rule specific to the collection (e.g., using the earlier example of facts about the solar system, items dealing with the identity of the planets would be presented before items dealing with the chemical composition of individual planets), and a rule determines when a session number can be incremented. The purpose of these rules is to organize and present material to be learned so as to first enhance recall of material (P-Level Items) already in the user""s memory before presenting 0-Level Items, which in turn are presented prior to new material (Unseen Items) to be learned, and also to present material in a way that will complement other learning materials, such as a textbook.
It is possible to use other means to apply the method of the present invention; means such as flash cards with an indexing system, for example, can be used to present the items and to place items into the appropriate sets.
The present invention is a method of presenting material to be learned to a user in such a manner that new or not-yet-mastered material is presented to the user repeatedly until the user has attained a threshold degree of mastery of it. The xe2x80x9cmasteredxe2x80x9d material is then presented with ever-decreasing frequency, as long as the user continues to recall it. Thus, the user is queried on new and not-yet-mastered material at a relatively high frequency (in terms of sessions) and queried on old and mastered material in ever-decreasing frequency (increasing time intervals). This method of reiterative presentation of material that the user has demonstrated that he or she has learned enhances long-term retention. The method allows a student to work at his or her own pace. Furthermore, the method is efficient in that it presents the student with material that is not-yet-learned and does not unnecessarily present already-learned material, other than at controlled intervals as a means of enhancing long-term retention of that material. A complementary feature of the present invention is its score-keeping and performance tabulation permitting the student or the student""s teacher to monitor the student""s performance.


A device is provided. The device includes a processor, a screen, and a memory including an application configured to record, transmit, receive, play, display, and group visual messages. Visual messages include a video, a snapshot, a reference to the video or snapshot, a drawing, audio content, a reference to the drawing or audio content, and a timestamp, a time reference within the video, a Global Positioning System coordinate, a user ID, a participant ID, or a reference to the timestamp, GPS coordinate, user ID, and participant ID. The application displays and maintains drawings on the screen for an amount of time not related to a duration of a video. The video and snapshot are recorded as part of an original video or snapshot visual message, and the drawing and audio content are not embedded in the video or the snapshot and are recorded as part of the visual message.

With the introduction of relatively low cost, high capacity broadband telecommunication services in the late 1990s, coupled with powerful computing processors and video compression techniques, videoconferencing has made significant inroads in business, education, medicine and media.
Videoconferencing is the conduct of a videoconference by a set of telecommunication technologies which allow two or more locations to communicate by simultaneous two-way video and audio transmissions. It has also been called 'virtual collaboration' and is a type of groupware. Videoconferencing differs from videophone calls in that it's designed to serve a conference or multiple locations rather than individuals. It is an intermediate form of videotelephony, first used commercially in Germany during the late-1930s and later in the United States during the early 1970s as part of AT&T's development of Picturephone technology.
Videoconferencing uses audio and video telecommunications to bring people at different sites together. This can be as simple as a conversation between people in private offices (point-to-point) or involve several (multipoint) sites in large rooms at multiple locations. Besides the audio and visual transmission of meeting activities, allied videoconferencing technologies can be used to share documents and display information on whiteboards.


The present invention provides a water repellant, water resistant, stain resistant fabric that feels like fabric rather than plastic. The fabric of the present invention is prepared by treating a fabric with at least one treatment composition comprising from about 5 weight percent to about 20 weight percent of fluorochemical(s), which is then backed with at least one polymeric film to provide a water repellant, water resistant, stain resistant fabric.

The present invention relates to treated textile fabric and to a method of treating a textile fabric. The present invention more particularly relates to a method of preparing a water resistant, water repellant, and stain resistant fabric, and to the textile fabric so prepared.
Stain resistance, water repellency and water resistance are important in many uses of textile materials. In restaurants, for example, table cloths and seating upholstery often lack stain resistance and are subject to rapid liquid, i.e., water, penetration. These properties necessitate frequent cleaning and/or replacement of such items. Although one generally views microbial growth as being associated with fibers of biologic origin such as cotton, wool, linen and silk, in the field of marine use, the high relative humidity renders even synthetic polymer textiles, such as polyesters and polyamides, subject to microbial growth, which is also true of many other outdoor uses.
The term xe2x80x9cwater resistantxe2x80x9d as used herein means essentially impermeable to liquids, such as water, i.e. treated textile fabric can support a considerable column of water without water penetration through the textile fabric. Such behavior is sometimes incorrectly termed xe2x80x9cwater repellant.xe2x80x9d However, the last term generally implies a lesser degree of water resistancy. Water repellency refers to the beading up and running off of water on a surface. Hydrophobicizing topical treatments are incapable of providing the necessary degree of water resistance as that term is used herein.
Textile fabrics may be made somewhat water repellant by various processes. For example, textile fabrics may first be scoured with a soap solution and then treated with a composition which may include zinc and calcium stearates as well as sodium soaps. The long chain carboxylic acid hydrophobic compounds provide a limited amount of water repellency. It is also possible to render fabrics somewhat liquid repellant by treating the fabric with commercially available silicone, for example poly(dimethylsiloxane).
To overcome problems associated with water absorption and stain resistance, resort has been made to synthetic leathers and polyvinylchloride (vinyl) coated fabrics. However, these fabrics do not have the hand or feel of cloth. Moreover, although attempts have been made to render such materials water vapor permeable, these attempts have met with only very limited success, as evidenced by the failure of synthetic leather to displace real leather in high quality seating and footwear.
Applications of relatively small amounts of fluorochemicals, such as the well known SCOTCHGUARD(trademark) to textile fabrics and similar compounds, also may confer a limited degree of both water repellency and stain resistance to the textile fabric. However, these xe2x80x9cSCOTCHGUARD(trademark) edxe2x80x9d textile fabrics are incapable of providing the degree of water repellency, water resistance, and stain resistance, as achieved by the present invention. Other methods of providing water repellant fabrics include coating the top surface of fabrics with thick polymeric coatings. These polymeric coatings, being on the top surface of the fabric, completely destroy the hand and feel of the fabric. Examples include vinyl boat covers, where the fabric backing is rendered water repellant by application of considerable quantities of polyvinylchloride latex or the thermoforming of a polyvinyl film onto the top of the fabric. The fabric no longer has the hand and feel of untreated fabric, but is plastic-like. Application of polyurethane films in the melt has also been practiced, with similar results. Moreover, unless aliphatic isocyanate-based polyurethanes are utilized, the coated fabric will rapidly weather.
The applicants of the present invention developed a treated fabric known as CRYPTON(trademark) which is disclosed in U.S. Pat. Nos. 5,565,265 and 6,024,823. The Crypton(trademark) fabric is liquid repellant, liquid resistant, stain resistant and antimicrobial. The Crypton(trademark) fabric is prepared by topically treating a fabric with a first, relatively low viscosity, aqueous treatment composition comprising an antimicrobial agent and a substantial amount of fluorochemical treatment composition. After passing through the first bath, the fabric is dried and cured, and then a relatively high viscosity treatment composition is knife-coated on the backside of the fabric to further treat the fabric, which is then dried and cured again. This knife coat treatment can be done once, or more than once.
It would be desirable to provide a fabric that allows water vapor to pass through the fabric while prohibiting the passage of liquid. It would also be desirable to provide a method of producing a liquid repellant, liquid resistant, stain resistant fabric. It would further be desirable to provide a liquid repellant, liquid resistant, stain resistant fabric that retains its natural hand and texture, is easy to handle, and economical to produce. Moreover, it would be further desirable to provide a liquid repellant, liquid resistant, stain resistant fabric that can be made relatively cleanly and with relatively little expenditure of time and money.
The present invention provides a water resistant, water repellant stain resistant, aesthetically and tactile pleasing fabric that does not feel like plastic. The fabric of the present invention is prepared by treating a fabric with at least one treatment composition comprising from about 5 weight percent to about 20 weight percent of fluorochemical(s), with the treated fabric then being backed with at least one polymeric film to provide a water repellant, water resistant, stain resistant, fabric.
The water resistant, water repellant, stain resistant fabric of the present invention retains its natural xe2x80x9chandxe2x80x9d or texture and is therefore aesthetically and texturally appealing. The fabric of the present invention is also durable, easy to handle and economical to produce.
The fabrics useful in the present invention include, but are not limited to, woven, non-woven and knitted fabrics, and preferably yarn or piece dyed upholstery woven fabrics, of natural fibers, synthetic fibers and mixtures of natural and synthetic fibers. Suitable natural fibers include, but are not limited to, fibers of cotton, linen, ramie, silk, wool and the like. Suitable synthetic fibers include, but are not limited to, fibers of nylon, polyester, acrylic, rayon, acetate and the like. Suitable fabrics for use with the present invention include, but are not limited to, jacquards (i.e., fabrics manufactured from a jacquard loom), brocades, dobbys (i.e., fabrics manufactured from a dobby loom), prints, poplins, cross-dyes, crepes, and canvases.
The treating process of the subject invention involves, in a first step, treating the fabric with a penetrating aqueous treatment composition, hereinafter referred to as the treatment composition. The treatment composition, in its most basic nature, comprises a substantial amount of a fluorochemical treating agent, and water. The treatment composition may preferably include one or more antimicrobial agents, such as microbioicides and/or mildewcides. The nature of the treatment composition is such that the fabric is thoroughly treated by topically treating the fabric, the treatment composition covering equally well both sides (i.e., surfaces) of the fabric as well as the surfaces of the fabric to cover the interstitial spaces within the fabric. The fabric is then oven dried and cured at elevated temperatures, for example, from 250xc2x0 F. to 350xc2x0 F. (121xc2x0 C. to 177xc2x0 C.), resulting in a primarily treated fabric. The primarily treated fabric is stain resistant, water repellant, and water resistant. In addition, its tensile and tear strengths are markedly improved. Yet, the primarily treated fabric is very difficult to distinguish from untreated fabric by hand, feel, texture, or ease of handling.
Although the process described above creates a unique new textile material, i.e., the primarily treated fabric, the primarily treated fabric is generally not completely water resistant. Inspection of the primarily treated fabric against a light source reveals multitudinous xe2x80x9cpinholesxe2x80x9d which may ultimately allow water to pass through the fabric. To render the primarily treated fabric completely water resistant, one or more polymeric films are adhered to the back side of the fabric, depending on the desired degree of water resistance. The primarily treated fabric having one or more polymeric films adhered thereto results in a secondarily treated fabric.
A more detailed description of how to make and practice the present invention follows below. It should be understood that the term xe2x80x9cweight percentxe2x80x9d, as used herein with respect to the components of the compositions of the present invention, refers to the total weight (i.e., the xe2x80x9cwet weightxe2x80x9d) of the components of the compositions of the present invention and not to the weight percents of the solids or polymers (i.e., the xe2x80x9cdry weightxe2x80x9d) in the components of the compositions of the present invention, unless otherwise specified.
The process of treating fabric in accordance with the present invention involves the application of the treatment composition to the fabric. The application of the treatment composition is then followed by oven drying and curing, resulting in the primarily treated fabric.
The treatment composition minimally contains a fluorochemical textile treating agent and water. In preferred embodiments, the treatment composition may further include antimicrobial agents, a crosslinking agent, a fire retardant and/or smoke suppressant, and other additives and auxiliaries such as dispersants, thickeners, dyes, pigments, ultraviolet light stabilizers, and the like. It would not depart from the spirit of the invention to include a minor amount of a dispersible polymer latex. However, the viscosity of the treatment composition must be low enough that thorough penetration of the fabric can be obtained.
The fluorochemical textile treating agent is preferably a latex and comprises from about 5 to about 20 weight percent of the treatment composition, based on the weight of the treatment composition, more preferably from about 6 to about 12 weight percent, and most preferably about 10 weight percent. The fluorochemicals provide water repellency, water resistance and stain resistance and may comprise unbranded generic fluoropolymers. Suitable fluorochemical treating agents include, but are not limited to, the commercially available fluorochemical compositions SCOTCHGUARD(trademark) FC 255, SCOTCHGUARD(trademark) FC 214-230, available from 3M, and ZONYL(trademark) RN, ZONYL(trademark) 8070, and ZONYL(trademark) 8787, available from E. I. Dupont de Nemours, and mixtures thereof. ZONYL(trademark) 8070 is the most preferred fluorochemical treating agent for use in the treatment composition. The fluorochemical treating agent typically comprises from about 5 to about 25 weight percent solids, based on the weight of the fluorochemical treating agent, and preferably comprises from about 8 to about 20 weight percent solids, and most preferably comprises about 18.5 weight percent solids. The amount of fluorochemical treating agent used in the treatment composition of the present invention is considerably higher than that traditionally used for treating upholstery fabric to render it stain resistant.
A latex antimicrobial agent preferably comprises from about 0.25 to a bout 4 weight percent of the treatment composition, based on the weight of the treatment composition, and more preferably from about 0.40 to about 2 weight percent, a nd most preferably a bout 0.60 weight percent. By xe2x80x9cantimicrobial agentxe2x80x9d it is meant any substance or combination of substances that kills or prevents the growth of a microorganism, and includes antibiotics, antifungal, antiviral and antialgal agents. The most preferred antimicrobial agent is ULTRAFRESH(trademark) DM-25, available from Thomas Research. Another preferred antimicrobial agent is AMICAL FLOWABLE(trademark), available from Angus Chemical Company of Northbrook, Ill. Other antimicrobials, particularly fungicides, may be used. Suitable examples include, but are not limited to, various tin compounds, particularly trialkyltin compounds such as tributyl tin oxide and tributyl tin acetate, copper compounds such as copper 8-quinolinolate, metal complexes of dehydroabietyl amine and 8-hydroxyquinolinium 2-ethylhexoate, copper naphthenate, copper oleate, and organosilicon quarternary ammonium compounds.
Crosslinking agents suitable for use in the treatment composition include resins which are themselves crosslinkable. Preferably, the crosslinking agent is a latex. Preferred self-crosslinking resins are the various melamine/formaldehyde and phenol/formaldehyde resins and their variants. Such as WT-50(trademark), a product of the B. F. Goodrich Company and Astromel NW3A(trademark). The most preferred self-crosslinking agent is Astromel NW3A(trademark), a product of Astro Industries, a division of Borden Chemical Company, of Morganton, N.C., which comprises about 80 weight percent solids and 20 weight percent water. Suitable other self-crosslinking resins include, but are not limited to, phenol, melamine, urea, and dicyandiamide based formaldehyde resins, which are available commercially, for example, from the Borden Chemical Company, of Columbus, Ohio. Preferably the self-crosslinking agent is present in the treatment composition in an amount of from about 0.1 to about 3.0 weight percent, based on the weight of the treatment composition, and more preferably in an amount of less than about 1.0 weight percent. Most preferably, the self-crosslinking agent is Astromel NW3(trademark) and is present in the treatment composition in an amount of about 0.25 weight percent, based on the weight of the treatment composition. Other crosslinkable resins such as oligomeric unsaturated polyesters, mixtures of polyacrylic acid and polyols, e.g. polyvinylalcohol, aliphatic and aromatic polyurethanes and epoxy resins may also be used, together with any necessary catalysts to ensure crosslinking during the oven drying cycle.
The primarily treated fabrics produced by the subject process can have flame retardants and/or smoke suppressants added to them to improve the flame retardency of the fabrics. Suitable flame retardants are known to those skilled in the art of fabric finishing, and include, for example, cyclic phosphorate esters such as Antiblaze(trademark) 19T available from Mobil Chemical Co.
The treatment composition is prepared by mixing the antimicrobial agent, the fluorochemical treating agent, the crosslinking agent and any other ingredients in water until a uniform dispersion is obtained. The water is present in the treatment composition in an amount of from about 70 to about 95 weight percent, based on the weight of the treatment composition, and more preferably from about 80 to about 90 weight percent, and most preferably about 84-89 weight percent.
The fabric to be primarily treated may be drawn through a bath of the treatment composition by any convenient method, or the treatment composition may be sprayed or rolled onto the fabric. Preferably, the fabric, previously scoured to remove textile yarn finishes, soaps, etc., is drawn through a bath of the treatment composition, as the treatment composition should uniformly coat both surfaces of the fabric as well as its interior. The fabric, after being drawn through a bath of the treatment composition, may be passed through nips or nip rollers to facilitate more thorough penetration of the treatment composition into the fabric and/or to adjust the amount of the treatment composition relative to the fabric (i.e. wet pickup). By such or other equivalent means, the wet pickup is adjusted to provide from about 30 to about 200 weight percent wet pickup relative to the weight of the untreated fabric, more preferably from about 60 to about 150 weight percent, and most preferably from about 80 to about 120 weight percent. About a 100 weight percent addition of treatment composition relative to the weight of the untreated fabric is considered optimal with, normal treatment composition solids content.
The coated fabric is then passed through an oven maintained at an elevated temperature, preferably from 250xc2x0 F. to 350xc2x0 F. (121xc2x0 C. to 277xc2x0 C.) for a period of time sufficient to cure the applied treatment composition. By the term xe2x80x9ccurexe2x80x9d, as used in the previous sentence, it is meant to dry the applied treatment composition, and, if the first application of treatment composition is not to be followed by additional treatments, to perform any necessary crosslinking of the components of the treatment composition. Generally, a period of from about 1 to 8 minutes, preferably about 2 minutes at 325xc2x0 F. (163xc2x0 C. ) is sufficient.
The primarily treated fabric of the subject invention has a number of advantageous and unique characteristics. It is highly, although not totally, water resistant, as well as being water repellant and stain resistant. While being highly water resistant, the primarily treated fabric allows ready passage of water vapor, and is thus eminently suited for items such as boat covers, which have traditionally been made of vinyl top coated fabrics. The vinyl top coated fabrics are substantially water vapor impermeable, and contribute to mildew formulation in boats using such covers. The primarily treated fabric has substantially the same hand, feel, texture, and drape of uncoated fabric, and thus can be manipulated by traditional manufacturing techniques as well as being aesthetically pleasing. The primarily treated fabric is also considerably more resistant to tear and opening at needle holes, as well as having higher tensile strength.
To render the fabric more completely water resistant, one or more polymeric films are adhered to the back of the fabric, depending on the degree of water resistancy desired. The adherence of one or more polymeric films to the back of the fabric is designed to render the fabric virtually totally water resistant. The polymeric film being adhered to the back of the fabric does not appreciably interfere with the hand and feel of the fabric. Moreover, the adherence of the polymeric film to the back of the fabric does not interfere with the aesthetic qualities of the fabric as the polymeric film is generally hidden from view during its preferred use, such as seating upholstery, curtains, etc.
The polymeric film can be any film formed by any fabrication technique known in the art, and may preferably be an extruded or cast film. The thickness of the polymeric film will generally range from about 0.5 mils (0.013 mm.) to about 10 mils (0.26 mm.) although thinner, as well as thicker, films can be used, if desired.
The polymeric film may be made of any curable or crosslinkable polymer, copolymer, blend, and the like, of polymeric material. Such polymeric materials can include, for example, and not by way of limitation, thermosetting and thermoplastic materials such as polyvinyl chloride, polyesters, polyamides, nylon, polysulfones, polyethylene, polypropylene, polychloroprene (neoprene), polystyrene, polymethylstyrene, polyethylene terephthalate, polyisoprene, polyvinyl acetate, polyvinylidene chloride, silicone resins, styrene-acrylonitrile copolymer resins, aliphatic and aromatic urethanes, and/or acrylates and their oligomers, polymethacrylates, isobornyl acrylate, polymethylmethacrylates, diol diacrylates, styrene-butadiene copolymers, polycarbonates, polycaprolactams, natural rubber latex, and blends thereof and coextrusions thereof. Other film forming materials will be obvious to those skilled in the art and are intended to be covered in the scope of the compositions, articles, and processes of the present invention.
The polymeric film can be adhered to the back of the fabric by any technique known in the art. One suitable technique in which the polymeric film can be adhered to the back of the fabric is employing the use of a thin suitable intermediate hot-melt adhesive layer (i.e., film of web) between the polymeric film and the fabric.
The intermediate hot-melt adhesive layer can be laminated between the fabric and the polymeric film by any known technique. The polymeric film is generally supplied from a roll of preformed polymeric film and a thin layer of hot-melt adhesive is melted between the fabric and polymeric film. The hot-melt adhesive is applied usually in an amount in the range of from about 0.25 to about 3 oz./yd2 (9 to 100g/m2) depending upon the adhesive although, less or more adhesive could be used, if desired. The adhesive, after being heated, is then be allowed to cool, preferably at room temperature, to secure the polymeric film to the fabric.
Suitable hot-melt adhesives include, but are not limited to, hot-melt adhesives comprising at least one polyamide, polyester, polyolefin, polyurethane and combinations thereof. It should be noted that a bi-component film could be used to simplify the securing of a polymeric film to the fabric. In a bi-component film, the hot-melt adhesive is provided preformed on one side of a polymeric film.
Adhesives other than hot-melt adhesives (such as liquid adhesives) can also be used. Suitable liquid adhesives for use are well known in the art. Some examples include plastisol, epoxy, acrylic, organosol and urethane adhesives. The liquid adhesives can be applied to the polymeric film by known coating techniques (gravure cylinder, knife, roller, reverse roller, anilox roller etc.), laminated under heat between the film and the fabric and allowed to cool to secure the film to the fabric. Plastisols are one of the best known liquid adhesive materials. These are dispersions of finely divided polymeric materials in nonvolatile organic liquids and low melting solids, generally referred to as plasticizers. Suitable plasticizers include phthalate, adipate and sebaccate esters and polyols such as ethylene glycol and its derivatives. A typical plastisol composition is between about 50 to about 95 parts polymeric material and about 5 to about 50 parts plasticizer. After the plastisol is deposited on the polymeric film, the film and the fabric are married (i.e., brought into contact with each other) so that the plastisol is disposed therebetween. Heat is then supplied to raise the temperature of the plastisol to above about 300xc2x0 F. to about 400xc2x0 F.  F to form a solid layer of PVC adhesive between the polymeric film and the fabric.
Another suitable technique in which the polymeric film can be adhered to the back of the fabric is to directly attach the polymeric film to the fabric without the use of an intermediate adhesive layer. This can be done in any suitable manner known in the art. Examples of suitable techniques include direct calender lamination and extrusion lamination. These techniques can produce a composite article without the use of an intermediate adhesive layer. In these fabrication techniques, the polymeric film acts as the adhesive because it is brought in contact with the fabric shortly after formation before the polymeric film completely cools. A mechanical bond forms between the fabric and the polymeric film when the polymeric film cools.
In direct calender lamination, the polymeric material is squeezed between two rollers to form a polymeric film. The fabric is fed off of another roller so that the fabric passes directly under the calendered polymeric film to receive the calendered polymeric film before the polymeric film completely cools. The fabric and its polymeric film can then be fed through pressure rollers to facilitate a more thorough penetration of the polymeric film into the fabric. A mechanical bond forms between the fabric and polymeric film when the film cools thereby securing the film to the fabric. The fabric and film can then be taken up on a roll.
Direct extrusion lamination is somewhat similar to direct calendar lamination. The main difference is that, in direct extrusion lamination, the polymeric film is extruded through a die onto the fabric, rather than being calendered onto the fabric.
Another suitable technique in which the fabric can be coupled with a polymeric film is to deposit, a plastisol or a similar material, such as organosol, onto the fabric and then to cure the deposited plastisol material to form a polymeric film adhered to the fabric. Depositing plastisol material directly onto the fabric works best when the fabric is relatively smooth. For relatively course fabrics, the plastisol material may first be deposited on a smooth carrier surface, such as a silicone release paper, and then be transferred to the fabric after the plastisol begins to gel, but before solidifying.
It is preferred that the primary treatment precede the application of the polymeric film(s) to the fabrics. However, the polymeric film(s) could be adhered to the fabric before the primary treatment or polymeric film(s) could first be adhered to the fabric, followed by the primary treatment, which could then be followed by adhering addition polymeric film(s) to the previously adhered polymeric film(s).
As mentioned above, the fabric of the present invention is durable, easy to handle and economical to produce. Because the fabric of the present invention retains its xe2x80x9chandxe2x80x9d or texture (i.e., does not feel like plastic), the fabric is easy to sew and seams are less noticeable, and more durable. For example, when vinyl is sewed, the needle holes tend to open when the vinyl is stretched. With the fabric of the present invention, needle holes do not tend to open and thus the seams are stronger and less noticeable. Moreover, while the fabric of the present invention provides a moisture barrier, it is believed that vapors are allowed to pass through the fabric. Human skin which may come in contact with the fabric of the present invention, for example in upholstery applications, is therefore less likely to perspire. The fabric of the present invention may also be transfer printed.